The $300 million deal, which incorporates the Great Noligwa underground mine and related infrastructure, is expected to boost Harmony's operational cash flow by 60%.
The company also said that ore from its Cigar Lake mine, in Canada's Saskatchewan, would not be milled until early 2015, instead by the end of the year.
But the International Atomic Energy Agency (IAEA) failed to disclose what the missing materials were, or whether it knew about them before they disappeared.